Developments in the electronics industry require the use of more densely packed electrical modules and circuits, each requiring multiple interconnections to one another. However, there is a practical limit to the density that can be achieved using conventional connective networks. In a typical present day application, a floppy disk drive may require a connection to a recording head whose conductors are only on the order of 0.2 mm (0.008 inches) on center and associated jumper conductors must have a similar spacing. Further, recent liquid crystal displays have conductors which are even more closely packed, for example, 0.1 mm (0.004 inches) on center, with similar requirements for interconnection conductors. In addition, there is growing use of ceramic PC boards to accommodate multiple IC chip arrays which also require high density connectors and custom interconnect cables for purposes of terminating those components.
As a direct result of the growth in the circuit board industry, there has been a parallel increase in the volume of environmentally-hazardous chemicals generated by the conventional etching and deposition processes. For example, it is not uncommon for one circuit board fabrication facility to generate 4,000 liters (1,000 U.S. gallons) per day of photo resist stripper and 4,800 liters (1,200 U.S. gallons) per week of developer solution. These toxic wastes must be transported off-site for proper disposal at hazardous waste management sites. Thus, there is an urgent need for a non-chemical method for the manufacture of conductive networks.
It is an object of this invention to provide a relatively inexpensive, high-quality, densely packed, supported conductive network for use in fabricating rigid or flexible circuit boards, that can be built without the use or generation of environmentally hazardous chemicals.
Another object of the invention is to provide a flexible conductive network having conductive paths which are profiled to self-align with corresponding conductors of other conductive networks.
Yet another object of the invention is to provide methods of making conductive networks having one or more of the above advantages.